netfilter: x_tables: make sure e->next_offset covers remaining blob size

Otherwise this function may read data beyond the ruleset blob.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Git-repo: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git


Git-commit: 6e94e0cfb0887e4013b3b930fa6ab1fe6bb6ba91
Change-Id: I78ac6043166c21e47b83a3742e3bd95c6710c953
Signed-off-by: Ravi Kumar Siddojigari <rsiddoji@codeaurora.org>